Flyback transformer coil for television receiver

ABSTRACT

Flyback transformer coil for television receiver comprises surface-insulated wire windings having a plurality of wire layers, a plurality of layers of insulating material thereby to separate adjacent layers of wound wires, and an assembly of the wirings and interpositioned insulating material being impregnated with a liquid heat-setting 1-2 polybutadiene resin having a lower dielectric loss at both low and high temperatures, for example 20*-150* C., and heated and hardened, thereby to deposit a hardened layer of the resin in all the layers of the coil assembly. The present coil has a good water, moisture and burning resistances and good insulating efficiency.

United States Patent [7 21 Inventor Yohel Shlmlzu Nlahlnomlya, Japan [21] Appl. No. 22,138

[22] Filed Apr. 2, I970 [45] Patented Nov. 16, 1971 [73] Assignee Sanyo Electric Co., Ltd.

Moriguchi-shi, Japan [32] Priority Oct. 28, 1967 [3 3 Japan Continuation of application Ser. No. 771,297, Oct. 28, 1968, now abandoned.

[54] FLYBACK TRANSFORMER COIL FOR TELEVISION RECEIVER 3 Claims, 2 Drawing Figs.

52 u.s.c| 336/205, 336/206, 336/96 51 Int.Cl. ..n01 27 30 so FleldoISearch 336/96, 205, 206; 260/94.7

Primary Examiner-E. A. Goldberg ABSTRACT: Flyback transformer coil for television receiver comprises surface-insulated wire windings having a plurality of wire layers, a plurality of layers of insulating material thereby to separate adjacent layers of wound wires, and an assembly of the wirings and interpositioned insulating material being impregnated with a liquid heat-setting l-2 polybu: tadiene resin having a lower dielectric loss at both low and high temperatures, for example 2()l50 C., and heated and hardened, thereby to deposit a hardened layer of the resin in all the layers of the coil assembly.

The present coil has a goodwater, moisture and burning resistances and good insulating efficiency.

PATENTEBNOV 1 6 ISYI INVI-INTOR yoh'E/ y/w/zu ATTORNEY FLYBACK TRANSFORMER COIL FOR TELEVISION RECEIVER This is a continuation of Ser. No. 771,297 filed Oct. 28, 1968 now abandoned.

The present invention relates to a coil for flyback transformer of television receiver, and more particularly to an improved coil for flyback transformer having a good water and moisture resistance, good burning resistance and good insulating efficiency.

A flyback transformer is employed in a television receiver to couple the horizontal sweep signal from the horizontal output stage to the deflection yoke and to develop the high voltage necessary for operation of the cathode-ray tube. Such transformers also {conveniently perform ancillary functions such as developing horizontal flyback pulses for application to the AGC keyer and developing blanking pulses for application to the cathode-ray tube. The flyback transformer is thus a high-voltage, high-energy device and must be carefully designed to insure compliance with rigid safety standards.

In the prior art flyback transformer now employed throughout the industry, a layer wound coil employing a kraft paper tape or polyethylene terephthalate tape as the insulating material and being impregnated with wax material or heatsetting epoxy resin is used as the secondary coil or high-voltage coil for the flyback transformer.

In the secondary coil impregnated with the wax material, for example, microcrystalline wax, the wax material is melted at an elevated temperature, and thus the wax material starts to flow This results in an increase iri flyback transformer temperature and the insulation of the transformer is deteriorated.

Further, the wax material-impregnated coil tends to burn with an increase in flyback transformer temperature.

It is a practice to place a corona tire, a compound molding, around the outer surface of the secondary or high-voltage coil to prevent corona which would otherwise result in failure of the transformer.

In the wax material-impregnated coil, a high temperature and high pressure are applied to the coil when the corona tire is placed thereon, and as a result the coil tends to be deformed.

In the heat-setting epoxy resin-impregnated coil, the epoxy resin itself has a high dielectric loss at a high temperature, for example 60 or higher, and thus the flyback transformer temperature tends to be raised so that there often occurs burning of the transformer.

As an extensive study of the impregnating materials suitable for the flyback transformer coil, the present inventor has succeeded in eliminating all the above-mentioned troubles encountered in the conventional secondary or high voltage coil for the flyback transformer.

The object of the present invention is to provide a coil for the flyback transformer, which has a good water resistance, good moisture resistance, good burning resistance and good insulating efi'iciency.

The invention together with further objects and advantages will be understood by reference to the accompanying drawings in which:

FIG. 1 is a perspective view, partially in section, of a flyback transformer for a television receiver.

FIG. 2 is a sectional view showing the coil, insulating material and papers in accordance with this invention.

Referring to FIGS. 1 and 2, a coil assembly 1 comprises a primary coil 3 wound on the spool 2 and secondary coil 4 on another spool 5.

The coils comprise surface-insulated wire 6, and a plurality of wire layers 7 separated by layers of insulating material 8. As is conventional, the coil assembly is further equipped with a lead 9 and a cap 10 which transfer the high voltage from the secondary coil to a high-voltage rectifier (not shown). Reference numeral 11 is a corona tire.

According to the present invention, a coil consists of the I of the insulating material, and an assembly of the wirings and interpositioned. insulating material being impregnated with a liquid heat-setting 1-2 polybutadience resin having less dielec tric loss at both low and high temperatures, for example, 20- 150 C., and heated and hardened thereby to deposit a hardened layer of said resin in all the layers of the coil assembly.

In the present invention, the insulating material includes a paper tape 8 such as a kraft paper tape, polyethylene terephthalate tape and other tapes having a suitable insulating effect.

The liquid polybutadiene resin used in the present invention includes atactic 1-2 polybutadiene, a, (ii-polybutadiene glycol and a, fl-polybutadiene carboxylic acid, which are commercially available in trademarks Nisso-PB, Nisso-PGB" and Nisso-PBC respectively, those being manufactured by NihonSoda Co., Ltd., Japan. The liquid polybutadiene used in the present invention is a liquid viscous polymer having a number mean molecular weight of 1,000 to 5,000 specific gravity of 0.86 to 0.90 (d,'). The liquid polybutadiene resin itself undergoes cross-linking by auto-oxidation at the ordinary temperature by leaving the liquid polybutadiene resin in a film state in air, and a hardened film is thereby obtained. However, the hardening can be promoted by adding a very small amount of metal salt or peroxide as a catalyst or can be effected in avery short time, for example, 30 min., by heating the resin to to 150 C. The cross-linking of the liquid polybutadiene resin is based on an autoxidation mechanism in the presence of air or oxygen, which is similar to that of such a drying oil as linseed oil. A clear resin having a high hardness can be also obtained by adding a radical polymerization initiator to the liquid polybutadiene resin and heating the added liquid resin to 120 to 140 C. for 20 to 80 minutes.

' The thus obtained hardened resin has a high mechanical strength, high heat deformation temperature and high insulating efficiency as shown below:

Mechanical properties:

Density, g/cm. 0.94 0.97 Hardness (Shore D) 64 75 Bending strength, kg./mm. 3.0 3.5 (ASTM-D-790) Compression strength, kg./mm." 7.1 8.6 (ASTM-D-695) Impact strength (Charpy), kg.cm./cm. 4.5 5.2 I-Iygroscopicity 0.01 0.03% (60 C., 5 hr) Molding shrinkage 3.3 3.5 (linear shrinkage) Thermal property Heat deformation temperature: 200 C. (ASTM-D-648) (load: 264 lb/in) Electrical properties Surface resistivity l0 10 Q (ASTM-D-257) Volume resistivity: 10 10" O (ASTM-D-257) Dielectric constant 30 c./s. 2.7 (ASTM-D-l50) l mc./s. 2.7 (ASTM-D-ISO) tan 30 c./s. 0.002 1 mc./s. 0.002

In the present invention, it is preferable, in view of the productivity, to use a liquid polybutadiene consisting substantially of l-2 polybutadiene resin and harden the same by heatsetting to shorten the processing time.

The present invention is explained hereunder, referring to examples:

Example I A coil was prepared by winding a 0.12 D, polyurethane-insulated wire using a 0.08 mm.-thick kraft paper tape as an interlayer, insulating material. Then, the wound assembly was impregnated with a liquid l-2 polybutadiene resin, and heated to C. for 3 hours thereby to form a hardened layer of the resin in all the layer of the coil assembly. Then, a proper corona tire was place on the surface of the deposited resin layer in the ordinary manner thereby to prepare a high-voltage coil.

Example 2 A high voltage coil was prepared by winding a 0.12 polyurethane-nylon2insulated wire using a 0.8 mm.-thick polyethylene terephthalate tape as an interlayer insulating material. Then, the wound assembly was impregnated with a liquid l-2 polybutadiene resin and heated to 135 C. for 3 hours thereby to form a hardened layer of the resin in all the layers of the coil assembly. Then, a silicone rubber corona tire was placed on the surface of the deposited resin layer in the ordinary manner thereby to prepare a high-voltage coil.

The high-voltage coils prepared in examples 1 and 2 were incorporated into a flyback transformer in the ordinary manner, and various tests for determining the characteristics of the present high-voltage coils were conducted by incorporating the thus prepared flyback transformer into a television set. For comparison purpose, the conventional high-voltage coil for the flyback transformer was prepared according to the following manner and tested at the same time.

Preparation of the conventional high-voltage coil:

A coil was prepared by winding a 0.12 D polyurethane-insulated wire using a 0.08 mm.-thick kraft paper tape as an interlayer insulating material. Then, the wound assembly was impregnated with microcrystalline wax, and an adhesive was applied onto the side surface of the thus impregnated coil. Finally, the corona tire was placed on the surface of the coil in the ordinary manner thereby to prepare a high voltage coil.

1. Temperature rise test:

The flyback transformers were mounted on television sets, and the tests were conducted at an ambient temperature of 40 C. The results are given in the following table.

Sample No. Temperature rise Conventional Coil l 75.5 2 79.0

Coil according to I 69.2 Example I 2 62.9 Coil according to I 60.4 Example 2 2 57.4

2. Reduced pressure test:

Test (A): Insulating effects between the high pressure coil and core, and between coil layers of the flyback transformer were compared in a reduced pressure state. The testing procedure was such that the flyback transformer was placed in a pressure-reducible, closed vessel; the inside pressure was gradually reduced; and the atmospheric pressure at spark was measured (high voltage output 27 kv. The results are given in the following table.

Core used in the test (A) was replaced with a larger core and the pressure-withstanding time was measured (transformers left at the ordinary temperature were used).

The results are given in the following table.

Sample Result Conventional I No high-voltage output was obtained at 350 mm. Hg for 20 seconds. and burning took place at 320 mm. Hg after 4 minutes 2 Spark was observed between a highvoltage coil heater and bobbin at 350 mm. Hg and test failed to continue No abnormal state was observed at 350 mm. Hg for 30 minutes Coil according to example I Coil according to example 2 Same as above Result Conventional Cracks were developed in the (Microcrystalline wax test piece wax) l-2 Polybutadiene No abnormal state such as cracks was observed 4. Boiling test: Boiling test of the high-voltage coils was conducted to compare water-resistance of coils. Coils were boiled for 1 hour and 30 minutes, washed with water for 30 minutes, and left in air for 1 hour and then aged. The results are given in the following table Output Just after After 10 After 15 mountln minutes minutes Sample (KV (KV) (KV) Conventional coll g g 5. g 52:8 0011 according to 1 25. 5 26. 5 25. 5 Example 1 2 23.0 23.0 23.0

. 5. Life test:

Flyback transformers incorporating a high-voltage coils prepared according to examples were mounted on television sets, and an SOD-hour continuous test was conducted at an overload condition to check the life of the coil, but no abnormal states were observed. The ambient temperature was 4 1 to 43 C.

As is clear from the result of the foregoing tests, the present coil is excellent in water-resistance, moisture resistance, insulating efficiency, etc., and since the resin having a less dielectric loss at both low and high temperatures, for example, 20- C., is used as an impregnating material, the temperature rise of the flyback transformer is so low that no burning of coil takes place.

Further, as the heat-setting impregnating resin is used, there is no disadvantage of fluidization as seen in the conventional wax, and the coil is not deformed even by application of heat and pressure thereto when a corona tire is placed thereon. Thus, a coil having a uniform and high quality can be prepared. Furthermore, impregnation, baking or other working can be readily conducted in preparing a coil.

As stated above, the present coil has various distinguished effects and utility over the conventional coil.

1. A coil for flyback transformer for television receiver, which comprises surface-insulated wire windings in a coil form having a plurality of wire layers, a plurality of layers of insulating material, adjacent layers of wound wires being separated by a layer of said insulating material, a corona tire attached to said coil, and an assembly of the wirings and interpositioned insulating material being impregnated with a resin consisting essentially of a polybutadiene in which said polybutadiene consists essentially of l, 2 polybutadiene having a specific gravity of about 0.86 to about 0.90 and a mean molecular weight of about 1,000 to about 5,000 said resin being heat hardened and having a low dielectric loss factor at both 20 C. and C and a shore D hardness between 64 and 75 in said heat hardened fonn, said resin having been applied in a liquid form.

2. A coil according to claim 1 wherein said heat hardened resin has a density (g./cm.) between about 0.94 and about 0.97, a bending strength (kg/mm?) between about 3.0 and about 3.5 (ASTM-D-790), a compression strength (kg./mm.) between about 7.1 and about 8.6.

3. A coil according to claim 1 wherein said insulating material is a kraft paper tape or polyethylene terephthalate tape.

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2. A coil according to claim 1 wherein said heat hardened resin has a density (g./cm.2) between about 0.94 and about 0.97, a bending strength (kg./mm.2) between about 3.0 and about 3.5 (ASTM-D-790), a compression strength (kg./mm.2) between about 7.1 and about 8.6.
 3. A coil according to claim 1 wherein said insulating material is a kraft paper tape or polyethylene terephthalate tape. 